Refining of lubricating oils



June 26, 1951 P, H, CARNELL 2,557,940

REFINING 0F LUBRICATING OILS Filed July 28, 1947 ATTORNEYS Patented June 26, ll

UNITED STATES PATENT QFFICE REFINING F LUBRICATIN G OILS Paul I-I. Carnell, Alma, Mich., assignor to Phillips Petroleum Company, a corporation of Delaware Application `luly 28, 1947, Serial No. 764,048

(ci. 19e-13) 17 Claims. 1

This invention relates to the treatment of lubricating oils to improve their properties. In one of its aspects it relates to the treatment of natural and/or synthetic lubricating oils to effect an improvement in their properties. In another aspect it relates to the treatment of such oils to increase their viscosity or viscosity index and to improve their color, gravity and other properties.

Lubricating oils of high quality have been manufactured from crude oil fractions having suitable boiling ranges by many processes including sulfuric acid refining, aluminum chloride refining, and solvent extraction. In sulfuric acid or aluminum chloride processes the treating reageants are consumed by reaction with the oil and are not economically recoverable from the resulting sludges. In solvent rening the action is simply one of separating high-quality lubricating ingredients from the crude oil or removing the undesirable or low-quality constituents. The use of solvents such as acetone, ethyl alcohol, ethyl acetate, furfural, etc., has been attended with serious faults and difhculties including lack of selectivity, miscibility of the solvent with water, high volatility involving nre hazard and substantial losses, low solubility of the oil in the solvent, instability, toxicity and poor separation of the solvent from the oil.

The prior art of the refining of lubricating oils with anhydrous liquid hydrofluoric acid shows (Frey U. S. Patent 2,378,762, issued June 19, 1945) that parafnic, mixed-base, or asphalt-base oil stock is improved by contacting such stock with liquid anhydrous hydrouoric acid and an alkylating agent or agents such as olens, cracked gasoline, alkyl halides, alcohols and unsaturated cyclics to form compounds of increased hydrogen-to-carbon ratio. Also my copending application, Serial Number 671,990, led May 24, 1946, now U. S. Patent No. 2,487,306, teaches refining lubricating oils with hydroiiuoric acid and a naphthenic compound.

The principal object of the present invention is to provide a novel and improved method of improving lubricating oils. Another object is to provide a method of improving natural lubricating oils. A further object is to provide a method 'of improving mixed-base lubricating oils. Another object is to provide a method of improving the viscosity index of natural or synthetic lubricating oils. Another object is to improve the viscosity index, color and pour point of lubricating oil. Another object is to provide a method of improving the properties of lubricating oils by a low-temperature treatment with substantially anhydrous hydrofluoric acid and a phenolic compound or derivative thereof. A further object is to provide a method of improving lubricating oils by a relatively high-temperature treatment with hydrofluoric acid and an isoparafn and a subsequent low-temperature treatment with hydroluoric acid, an isoparafiin and a phenolic compound. Numerous other objects will be apparent from a study of the annexed drawing and the following specification and discussion.

The accompanying drawing illustrates diagrammatically one embodiment for the practice of the present invention.

Broadly speaking, my invention is a process of improving lubricating oil which comprises contacting the lubricating oil with substantially anhydrous hydroiluoric acid and a phenolic compound at a relatively low temperature and recovering the lubricating oil from the resulting mixture. In one modification of the invention the lubricating oil may be primarily treated with hydrofluoric acid and an alkylating hydrocarbon such an an isoparan at higher temperatures. Preferably the lubricating oil is subjected to the higher-temperature treatment with hydrofiuoric acid and the isoparafiin and then to the low-temperature treatment with recycle hydrouoric acid and recycle isoparaifln from the high-temperature treatment and with a phenolic compound, such as phenol, cresol, xylenol, anisole, phenetole, diphenyl ether, etc. y

Petroleum and crude lubricating oils from petroleum are essentially a mixture of hydrocarbons comprising groups of homologous series of compounds such as the parains, hydroaromatics, aromatics, high molecular weight polymethylenes, derivatives of all of these classes, and various otherv series in which the hydrogen-to-carbon ratio is even lower than in the above classes, A large number of individual compounds of each series are prevalent in crude petroleum oils but have different boiling points, physical and chemical properties. The crude oils are generally classified as paraihn-base, naphthene or asphaltbase, and mixed-base oils, the various series of hydrocarbons being present in varying proportions. The parain-base oils contain a relatively high proportion of parafnic hydrocarbons having chain structures and high hydrogen-to-carbon ratios and the naphthene-base oils contain a high proportion of aromatic hydrocarbons with ring structures of comparatively low hydrogento-carbon ratios. The mixed-base oils are, in general, intermediate between these two extreme C; types. In the normal rening of crude petroleum, the fractions of varying distillation ranges show the saine characteristics as the oil from which they are obtained and the crude lubricating oils recovered from crude petroleum stocks show the same characteristics as the crude petroleum from which they are derived.

The lubricating oils which are beneted by the present process include paranic oils, mixedbase oils, and asphalt-base oils but are preferably the mixed-base oils. Synthetic lubricating oils, such as those prepared by the polymerization of oleiinic hydrocarbons, may also be improved by the present process. A most important improvement in the oils treated by the present process is in the viscosity index, which is determined by the method described in an article entitled Viscosity Variations of Oils with Temperatures, by E. W. Dean and G. H. B. Davis, in Chemical and Metallurgical Engineering, volume 36, page G19 (1929). The viscosity index of a lubricating oil is an indication of its composition or type, that is, whether it is a paraffin-base or naphthene-base oil. Paranin-base oils have high viscosity indices, naphthene-base oils have relatively low viscosity indices and mixed-base oils have viscosity indices between these extremes. This index is likewise a measure of the ability of a lubricating oil te remain viscous at high temperatures; as is well known, oils lose rapidly their viscosity with an increase in temperature. The oil with a high viscosity index will, however, lose its viscosity less rapidly than an oil with a low viscosity index when the temperature is increased. The present invention increases this viscosity index and may also increase the absolute viscosity at the standard 210 F. temperature for measurement of viscosity.

Crude lubricating oil stocks vary widely in composition. The various compounds may be classified in the following groups: asphalt; resins; naphthenes; cyclo-alkyl compounds; parafiins, including wax; and color bodies.

Asphaltic constituents are tarry or pitchy materials of aromatic structure. Resins are similar but of lower molecular weight and more soluble in paraffin hydrocarbons. These constituents cause sludge and varnish formation in motor oils, and therefore must be removed by oil-refining processes.

By naphthenes is meant saturated liquid hydrocarbons which are predominantly cyclic in structure. Such hydrocarbons have good lubricating properties for use at constant temperatures, but the viscosity index is low; that is, the viscosity varies greatly with the temperature.

The cyclo-alkyl compounds are hydrocarbons having one or more cyclic nuclei with aliphatic chains attached thereto.

The parai'lns have very high viscosity indices, and good lubricating properties. As many of the paraflins present in lubricating oil stocks have high melting points, the proportion of paralins which may be present in the final lubricating oil is limited mainly by the maximum permissible pour point of the oil. The allowable proportion of parafns may be increased somewhat by using pour point depressants.

The structure of the color bodies is not fully known. They have been described in literatureV as being neutral resins, asphaltenes, and cyclic bodies having unsaturated side chains, such as the fulvenes, etc., and are objectionable mainly because of consumer demand for oil of clear and standard appearance.

Treatment of lubricating oils according to the present invention raises the viscosity index, increases the API gravity, and improves the color. Although the exact nature of the changes which take place in the oil is not known, the low-temperature treatment selectively dissolves out the resins and asphaltic materials and the presence of the phenolic compounds furthers this solvent action. In addition, the hydrofluoric acid promotes the separation of the parainic and the nonparaiinic hydrocarbons so that recovery of the lubricating oils and treating agents is more rapidly and thoroughly accomplished, as more fully discussed hereinafter.

I-Iydrofluoric acid is a preferred acid in the present invention because in addition to having a rening action on the oil it is easily separated from the oil extracts by a simple distillation and, furthermore, under the relatively mild conditions of solvent rening it does not react with the solvents conventionally employed. The use of hydrouoric acid in conjunction with the phenolic solvents of the present invention is also advantageous because lower temperatures may be employed in the low-temperature refining step and separation of the solvent from the refined lubricating oil is facilitated by its ready solubility in the acid. Furthermore, any HF remaining in the treated oil and the HF in the solvent is easily removed from the mixture by distillation.

As mentioned before, the phenolic compounds employed in the practice of this invention include phenol and phenolic derivatives such as cresol, Xylenol, anisole, phenetole, diphenyl ether, as well as cresylic acid, tricresyl phosphate, and substituted derivatives of these compounds. The mutual solubility and non-reactivity of the hydroluoric acid with these phenolic solvents act to cause a more rapid and thorough separation of the lubricating oil and the treating agents.

The isoparafns employed in this invention usually comprise the low-boiling isocornpounds of four to six carbon atoms, and isopentane has been found to be particularly desirable. The isoparafn added may be any one of the group or a mixture of the desirable isocompcunds, as well as a concentrated hydrocarbon fraction of one or more of the desirable compounds. In addition to any chemical change eiected, these compounds aid the hydroiiuoric acid and phenolic solvent in attaining intimate contact and in the precipitation o asphaltic compounds from the oils. Although the full signicance of the chemical reactions occurring in the treatment described is not fully understood, the presence of the isoparafns in the initial higher temperature treatment, when employed, may provide additional desirable cycloalkyl constituents to the product oil through reaction of the isoparaiiins with some of the cyclic compounds present.

The low-temperature treatment of the present process is conducted between about -20 and 30 C. At these temperatures the solvent eiect of the hydrouoric acid and the phenolic solvent is highly effective and the undesirable asphalts and resins in the oil dissolve readily in the hydrofluoric acid and solvent and may be removed therewith.

The pressure may vary widely but should be suficient to hold the hydronuoric acid and the hydrocarbons in liquid phase throughout the reaction. The pressure may vary from atmospheric pressure to 759 pounds per square inch or higher depending on thetemperature conditions and the reactants employed, but in the lower-temperature treatment will generally be only slightly superatmospheric.

In general, the contact time may range from about ten minutes to two hours. Reaction time will, of course, depend upon the temperature ol' the treatment and on the particular reactants employed. In the primary high-temperature treatment of the lubricating oils, as discussed above, conditions of treatment generally comprise contacting the lubricating oil with the isoparain in the presence of hydroluoric acid between about 100 and 300 C. for a contact time of to 120 minutes or more in a volume ratio of hydrouoric acid to oil to parainn of approximately 121:1. In both steps of the treatment, it is preferred to have sufficient acid present to maintain a separate liquid hydroiluoric acid phase at all times, so that a favorable volume ratio of oil, isoparaflin, liquid acid, and solvent may be about 3, 3, 2, and l, respectively.

Where desirable a separation of the reactants may be made between the high-temperature and the low-temperature treatment when both are employed, with the recycle of separated hydroluoric acid, isoparaiin and low molecular weight cycloalkyl compounds formed in the process and with the separation of acid-soluble compounds from the acid before recycle to the process.

When desirable, a diluent hydrocarbon may be employed to dilute the mixture of oil and treating agents and to facilitate contacting of. the lubricating oils with the treating agents. In general, however, the isoparaflin which is employed in the process will provide suicient diluent effect, although further diluents may be employed where desirable. Such diluents will generally be condensable paraflins such as liquid propane, liquid normal butane, normal pentane or normal hexane.

Any suitable equipment may be employed for the performance of the present invention and equipment which is resistant to the corrosive action of hydroiluoric acid is particularly desirable. Conventional contacting equipment similar to contactors which are commonly used for conducting the alkylation of aliphatic isoparains and olelns may be used to provide suitable contact between the reactants. One example is the so-called Stratco contactor. Any other means of maintaining an intimate contact of the hydrocarbon and acid phases may be employed. The equipment should be provided with means for maintaining the desirable temperatures in the various zones. Other equipment such as valves, pumps and similar equipment necessary for accomplishing the process of the present invention will be familiar to those skilled in the art and have been omitted from the drawing for simplicity.

In the performance of the present invention lubricating oils from various sources may be treated according to the process described above, allowed to separate, usually by gravity, into two separate layers, namely a lower layer containing the acid and solvent which is recycled yand an upper hydrocarbon layer. The hydrocarbon layer may be topped under vacuum to remove hydrocarbons lighter than the untreated oil, if desired. The lighter hydrocarbons, which may include any unreacted isoparaffins, may then be recycled to the process. When the higher temperature treatment is employed before the lowtemperature treatment, the lubricating oil may be first treated in a reaction zone in the presence of the isoparain and substantially anhydrous hydrofluoric acid at the higher temperatures and then separated with a recovery of the hydrocarbon layer which is directed to the low-temperature treatment and with the recovery of an acid phase which is'further separated into recycle hydroliuoric acid and into acid-soluble oils `which are removed from the system. The hydrocarbon layer with a portion of the recycle acid is eX- tracted with a phenolic solvent in the low-temperature treatment, after `which it is separated into the lower acid phase containing the acid, the solvent, and the acid-soluble oils and the upper hydrocarbon phase which is separated into recycle isoparailn and other relatively low' molecular weight compounds which are formed, such as cycloalkyls, and into the improved lubricating oil. y

The process may be carried out either inv a batchwise manner or continuously, the latter being preferred for commercial operation. `Although the present invention particularly teaches the advantages of the low-temperature treatment of a lubricating oil in the presence of substantially anhydrous hydrouoric acid and a phenolic solvent, a better understanding of the invention may be had by reference to the accompanying drawing which illustrates an over-all process embodying an initial high-temperature treatment, which is a favored embodiment of the present process. In the initial step lubricating oil is introduced by line I-El into a reactor Il; hydrofluoric acid is introduced into the reactor by line I2 and yacid recycle line I3; andisoparain is introduced into the reactor through line I4 and recycle line l5. After a suitable contact time between about 20 to 120 minutes at temperatures between about 10G and 300 C. in reactor II, the mixture is `withdrawn through line I6 t0 a separator I'I in which the acid `and hydrocarbon constituents separate into layers by gravity. The acid is removed by line I8 to an acid-recovery fractionator I9 which may be operated under vacuum, if desired, and from which recycle acid is removed overhead through line I3. Solvent introduced in a subsequent step is recovered as an intermediate eluent and returned to the subsequent step by a line 20. Heavier acid-soluble compounds are removed as bottoms by line 2|. The hydrocarbon layer from separator II is passed through a line 22 into an extractor 23 whe-re it is thoroughly admixed with a portionof the recycle hydroluoric acid through line 24 and lwith a phenolic solvent from line 25. After thorough contacting at a temperature between about -20 and 30 C. for a period of about 10 to minutes, the adrnixture is withdrawn through line 2B to a separator 2l in which it is allowed to settle and separate into an upper hydrocarbon phase and into a lower acid phase containing the acid, solvent, and any acid-soluble compounds, such as acid-soluble oils. The acid layer is withdrawn through line 28 to the acid feed line I8 entering the acid-recovery fractionator I9 where a separation is made of the acid, the solvent, and the acid-soluble constituents as described. The hydrocarbon layer is separator 2l, containing the desired lubricating oil, is withdrawn by line 29 to a fractionator vIi where the hydrocarbon phase is topped to remove the lighter hydrocarbons from the treated lubricating oil which is recovered through aline 3 The lighter hydrocarbons,

vincluding the unreacted soparaliins and low molecular weight cycloalkyls and products formed during the treatment, may be removed overhead and recycled to the initial reaction zone through the recycle line I5, or from the system through line 32. Various valves, pumps, and other conventional equipment necessary for the successful practice of the invention will be familiar to one skilled in the art and have been omitted from the drawing for sake of clarity.

' As mentioned before the process may be practiced for the improvement of the properties of both synthetic and natur-al lubricating oils of various composition by employing only the lowtemperature extraction step or by a combination of the high-temperture and low-temperature steps, as described.

VFollowing are specic examples of the treatment of lubricating oils with hydrouoric acid in the presence of a phenolic solvent or a mixture 0f such soivent and an isoparain. 'Ihe procedure in Examples 1 to 5 was as follows:

A 4.5-liter steel bomb was charged with a mixed-based lubricating oil, liquid anhydrous hydrofluoric acid, a phenolic solvent, and, when desired, an isoparanin. The charged bomb was clamped to a rocker and Was itted with a suitable pressure gauge. The bomb was agitated at the desired temperature, usually room temperature, for the time recorded and was removed from the rocker and placed in a vertical position. V'lihe contents of the bomb were allowed to settle. The acid and hydrocarbon layers were separated, and the hydrocarbon layer was Washed with dilute caustic solution and separated. The hydrocarbon layer was then topped to the initial boiling point of the untreated oil to remove the low-boiling constituents.V

Examples 1 to 5 The results of experiments showing the benefits to be derived from the practice of this invention are shown in the following table which tabulates the results of five combinations of 24 hours, so that a comparable -product oil cannot be obtained to compare with the initial untreated oil.

In another experiment shown in Example 3, another sample of untreated lubricating oil is treated under the same conditions of time and temperature with hydrofluoric acid and isopentane but in the absence of a phenolic solvent, The results of this experiment show no change in the viscosity index but shows an improvement in the color and API gravity of the cil.

In a fourth experiment, Example 4, another sa-mple of the untreated lubricating oil is treated under the same conditions of time and temperature with hydroiiuoric acid, isopentane, and o-cresol. The results of this treatment show substantial improvement in the viscosity index as Well as in color, pour point, and API gravity.

In another test, Example 5, another sample of untreated lubricating oil is treated under the same conditions of time and low temperature with hydrofluoric acid, isopentane, and anisole. The results of this experiment conrms the improvements which can be expected from the lowtemperature treatment of lubricating oil with hydroiluoric acid, a phenolic solvent and an isoparaffin.

From a comparison of the results of the experiments in the preceding examples, the desirability of treating the lubricating oils according to the present process is evident in the last two examples which show a marked improvement in the viscosity index and ASTM color, as well as the API gravity, rating of a lubricating oil so treated. Furthermore, it is evident upon further examination that a marked improvement in viscosity index is effected upon the lubricating oil when treated under the conditions of Example l, namely, with hydroluoric acid in the presence of an isoparaiiinic compound treatment of a mixed-base lubricating oil. under a relatively high temperature. However,

Example Untreated oii Oil, gms 262 874 878 881 881. HF, gms... 1,771 922 613 608. Isoparain", Isopentane.- Isopentane Isopentane Isopentane. Isoparatlin, gms 992 620 25 630. Phenolic Solvent Phenolic Solvent, gms Contact Time, minutes.. Maximum Temp., C Product Oil:

Viscosity, 100 F. SUS 287. 3 253.0 Viscosity, 210 F. SUS 50. 77 49.8() Viscosity Index (Dean and Davis) 89 99 Pour Point, F +30 +35 API Gravity 28.7 31.2 ASTM Color 2% 2% 1 No separation of cresol from oil obtained after 24 hours.

A comparison of the various treatments in the above table shows that in a first treatment, Example l, the lubricating oil when treated with a large excess of hydrouoric acid and an isoparaiui (isopentane) in the absence of a phenolic solvent at high temperatures and excess pressure improves the viscosity index substantially and raises the API gravity, but leaves the color unimproved.

Under the conditions of a second experiment, Example 2 shows that the treatment of a lubricating oil with isopentane and a phenolic solvent (o-cresol), but in the absence of hydrofluoric acid, at a desirably low temperature of 25 C. and a contact time of two hours gives a mixture which does not separate even after a period of the color of the oil when treated in the manner of Example l is materially unaiected, so that the added improvement to be derived from effecting a material increase in viscosity index by a higher temperature treatment with hydrofluoric acid and an isoparafn combined with a low temperature treatment in presence of hydrouoric acid and a phenolic solvent to further increase the viscosity index and materially improve the color and other properties may be readily recognized from the discovery of the advantages of each treatment.

Although the process has been described and illustrated in terms of its preferred modications, it is understood that various modifications of the preferred process may be made and many 9 of the advantages of the refining process realized. For example, although the presence of an isoparaiiin is preferred during the high-temperature treatment, many valuable benets are realized by this high-temperature treatment in the presence of hydrouoric acid alone followed by the low-temperature treatment of the mixture with a phenolic compound or a phenolic compound and an isoparain. In this manner of treatment the hydroliuoric acid has a refining and improving action on the lubricating oil and, in addition to the supplemental rening effect of the isoparaiin and the phenolic compound in the subsequent step, the latter compound has a solvency action on the hydrofluoric acid so that the hydroiiuoric acid is more readily separated from the body of the oil, since the acid is preferentially soluble in the phenolic compound. If

an appreciable amount of the phenolic compoundA or other oxygenated compound is present in the oil after the treatment with and separation of the phenolic compound, it may be desirable to subsequently extract the mixture with substantially anhydrous hydrofluoric acid; any residual oxygenated compound may thus be removed and slight traces of the acid which do not separate from the oil may be readily dispelled by heating the body of oil.

The examples are given to compare the results of similar treatments and to show the superiority of the present process over the other modes of treatment. The examples are to be taken as illustrative only and are not intended to limit the scope of the present invention. iications and changes may be made in the process without departing from the spirit of the invention as recited in following claims.

I claim:

l. The process of improving the properties of a lubricating oil which comprises treating said oil with substantially anhydrous hydrouoric acid and an isoparaflin at elevated temperatures and pressure in a first step, cooling the treated mixture, adding and thoroughly admixing a phenolic compound with the cooled mixture in a second step to extract said oil and thereby improve its color, separating the admixture into an acid phase containing said acid and said phenolic compound and a hydrocarbon phase, and distilling said hydrocarbon phase to recover said improved lubricating oil.

2. The process of improving the properties of a lubricating oil which comprises contacting said cating oil of improved color and viscosity index l which comprises contacting said oil with substantially anhydrous hydrofluoric acid and an isoparainn at a temperature between about 100 and 300 C. for a conversion period between about and 120 minutes in a rst step, cooling the Various modi- Vtreated mixture and admixing a phenolic solvent therewith, thoroughly agitating the admixture for an additional 10 to 150 minutes at a temperature between about 20 and 30 C. in a second step to extract said oil and thereby improve its color, separating the admixtiue into a lower acid phase containing said acid and said phenolic compound and an upper hydrocarbon phase, and distilling said hydrocarbon phase to recover the improved lubricating oil.

4. The process of preparing a iinished lubricating oil of improved properties which comprises treating said oil in an initial conversion zone with anhydrous hydrouoric acid and an isoparafn at a temperature between about and 300 C. for a period between about 20 and 120 minutes in a rst step, separating the treated mixture into an acid phase and a rst hydrocarbon phase, passing said hydrocarbon phase to a solvent extraction zone, separating said acid for recycle from the acid phase in anacid-recovery Zone, adding at least a portion of the recycle acid to said extraction zone and recycling the remainder to the initial conversion zone, introducing a phenolic solvent into said extraction zone, thoroughly agitating the mixture of compounds in said extraction zone at a temperature between about -20 and 30 C. for a period between about 10 and 150 minutes in a second step to extract said oil and thereby improve its color, withdrawing the mixture from the extraction zone and separating the same into an acidphenolic solvent phase and a second hydrocarbon phase, recycling said acid-phenolic solvent phase to the acid-recovery zone to separate the acid and the phenolic solvent for recycle, distilling said second hydrocarbon phase to separate said improved lubricating oil from lighter hydrocarbons including unreacted isoparaffin, and recycling said lighter hydrocarbons to the initial conversion Zone.

5. The process of preparing a finished lubricating oil of improved properties which comprises contacting said oil at a temperature between about 100 and 300 C. with substantially anhydrous liquid hydrofluoric acid in a first step, cooling the mixture and admixing a phenolic compound therewtih, thoroughly agitating the admixture at a temperature between about -20 and 30 C. for a time sufficient to improve the properties of said lubricating oil in a second step to extract said oil and thereby improve its color, and recovering said improved lubricating oil from said acid and phenolic compound.

6. The process of improving the properties of a lubricating oil which comprises contacting said oil with anhydrous hydrouoric acid and an isoparafin at a temperature between 100 and 300 C. for a conversion period between 20 and 120 minutes in a first step'y cooling the treated mixture and-admixing a phenolic compound therewith in a second step to extract said oil with said acid and said phenolic compound, separating the admixture into an acid phase containing said acid and said phenolic compound and a hydrocarbon phase, extracting said hydrocarbon phase in a third step with added anhydrous hydrogen fluoride to remove residual quantities of said phenolic compound therefrom, and distilling the resulting hydrocarbon to recover said improved lubricating oil.

7. 'I'he process of preparing a linished lubricatasp'aeso Iing oil of improved color and viscosity index which comprises contacting said oil with anhydrous hydrouoric acid and an isoparain at a temperature between 100 and 300 C. for a conversion period between 20 and 120 minutes in a iirst step, cooling the treated mixture and admixing a phenolic solvent therewith, thoroughly agitating the admixture for an additional 10 to 150 minutes at a temperature between -20 and 30 C. in a second step to extract said oil with said acid and said phenolic compound, separating the admixture into an acid phase containing said acid and said phenolic compound and a hydrocarbon phase, extracting said hydrocarbon phase with added anhydrous hydrogen fluoride in a third step to remove residual quantities of said phenolic compound therefrom, and distilling the resulting hydrocarbon to recover the improved lubricating oil.

8. The process of claim 7 wherein the phenolic compound is o-cresol.

9. The process of claim 1 wherein said phenolic compound is phenol.

10. The process of claim 1 wherein said phenolic compound is cresol.

11. The process of claim 6 lwherein said phenolic compound is phenol.

12. The process of preparing a finished mixedbase lubricating oil of improved properties which comprises agitating a liquid mixture of said oil, van isoparaffinic compound having from 4 to 6 carbon atoms per molecule, anhydrous hydrogen fluoride and a phenolic solvent in the volume ratio of 323:21, respectively, at a temperature within the range of 20 to 30 C. and for about 2 hours, separating said mixture into an acid phase containing said acid and said phenolic solvent and a hydrocarbon phase, and recovering said improved oil from said hydrocarbon phase.

13. The process of claim 12 wherein said phenolic solvent is o-cresol and said isoparainic compound is isopentane and said temperature is 25 C.

14. The process of claim 12 wherein said phenolic solvent is anisole.

15. The process of claim 1 wherein said phenolic compound is anisole.

16. The process of claim 1 wherein said phenolic compound is diphenylether.

l. The process of claim 1 wherein said Vphenolic compound is tricresyl phosphate.

PAUL H. CARNELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,035,102 Stratford et al Mar. 24, 1936 2,145,828 Clarke et al. Jan. 31,1939 2,246,257 Kohn June 17, 1941 2,320,629 Matuszak June 1, 1943 2,378,762 Frey June 19, 1945 

1. THE PROCESS OF IMPROVING THE PROPERTIES OF A LUBRICATING OIL WHICH COMPRISES TREATING SAID OIL WITH SUBSTANTIALLY ANHYDROUS HYDROFLUORIC ACID AND AN ISOPARAFFIN AT ELEVATED TEMPERATURES AND PRESSURE IN A FIRST STEP, COOLING THE TREATED MIXTURE, ADDING AND THOROUGHLY ADMIXING A PHENOLIC COMPOUND WITH THE COOLED MIXTURE IN A SECOND STEP TO EXTRACT SAID OIL AND THEREBY IMPROVE ITS COLOR, SEPARATING THE ADMIXTURE INTO AN ACID PHASE CONTAINING SAID ACID AND SAID PHENOLIC COMPOUND AND A HYDROCARBON PHASE, AND DISTILLINING SAID HYDROCARBON PHASE TO RECOVER SAID IMPROVED LUBRICATING OIL. 